Approaches for combining handwriting acts and control by computer are gaining force. As two types of general classifications of these approaches, the “pen tablet” and the “digital pen” are often cited. As for the former approach, in addition to being able to display handwritten information, it can display drawing effects and additional information related to that information. Data output by this approach, however, can only be handled by digital-type displays. As for the latter approach, although written information acquired as paper input can be digitized, it is not possible to express additional information as output on paper (i.e., a paper display). In contrast to those two approaches, the system proposed by the authors — called “Hand-rewriting” — automatically performs “rewrite” processing on paper in correspondence with handwriting using pen and paper. More specifically, with the proposed system, when the user writes on a piece of paper with a pen, for example, the information written on the paper is automatically erased as required, and additional information is displayed on the paper in natural print-like colors.